Stephen King had that happen as well with his Dark Tower series. After he was hit by a car in 1999 he wrote the last three books relatively quickly, but they were of lower quality than the first four.
After I took ill in 2015, I decided I’d never start another book series that wasn’t already completed. I’ll leave enough unfinished when I go, I don’t want to add stories, books I’ve become immersed in, to the list. Butcher’s Dresden Files was what prompted that stance, and his five years in-between books has done nothing to change my mind.
Right , HBO was the ghost writer for him for the last 2 books.